13 



gcnous matter, producing' putrefaction, and therefore 

 substances of little or no feeding value. Those are some 

 of the changes which are liable to occur. Now., our en- 

 deavour is to preserve green fodder without allowing it to 

 undergo any change. That, at least, would be an ideal state 

 of things, and the nearer we can approach that state the 

 better, for all and any chemical changes which do occur 

 are of a destructive and degenerative rather than a forma- 

 tive and elaborative kind. 



In practice, however, it will be seen that it is impossible 

 for us to check action at the very beginning. But we can 

 prevent it going beyond a certain distance. 



We know that bacteria require water, a temperature 

 within certain degrees, and air. The moisture contained 

 in the fodder we cannot take away without converting the 

 stuff into hay and thereby defeating our object. We 

 cannot control the temperature by the methods used in the 

 preservation of milk and meat, for instance, as they would 

 be too expensive, but we can control to a certain extent the 

 amount of oxygen present, by pressing out more or less of 

 the air from the heap, and preventing the entrance of more. 

 We have said that it is impossible to check the action at the 

 very beginning, and the reason is clear, for a certain amount 

 of air is always contained in the interstices of the mass. 

 On this supply fermentation goes on of an alcoholic and 

 lactic nature till it can no longer be supported. The 

 temperature will have risen, acids will have been produced, 

 and the interstices will have been filled with a product 

 of fermentation, carbonic acid gas, and if no more air is 

 admitted no further action will take place. The mass will 

 keep for a number of years. The keeping of silage is due 

 principally to the large amount of volatile acids and 

 carbonic acid gas produced, which effectively prevents the 

 further growth of bacteria, and to the sterilization which 

 it has. undergone during the warmer stages of the 

 fermentation. 



We will now go on to the consideration of the different 

 systo.? in use for the manufacture of silage. 



